This invention relates to ceramic particles having shapes that are well adapted to use as abrasive grits and particularly to a process for the manufacture of such particles.
Abrasives particles are conventionally made by crushing larger pieces of the ceramic by a milling or roll crushing process. Such processes are highly energy intensive and result in particles with significant amounts of microfractures as result of the impacts that generated the particles. These microfractures are believed to be a source of weakness in the particles that reduce their effectiveness as abrasives.
When sol-gel processes were developed for the production of alumina abrasives, a gel is formed of a precursor form, usually boehmite and this gel is extruded of otherwise shaped into manageable pieces which are then dried to drive off the water. The dried gel, which is very friable, is then typically comminuted to approximately the desired range of particle sizes for the final abrasive particles and these particles are fired to produce the final abrasive particles.
Recently, in U.S. application Ser. No. 08/417,169 filed Apr. 5, 1995, it has been proposed to feed the dried gel while it still possesses at least 5% by weight of water content directly into the hot zone of a furnace to cause the water to expand explosively. This results in particles with a generally high aspect ratio and excellent abrasive properties.
It has now been discovered that a wide range of ceramic materials can be caused to comminute explosively to produce similar high aspect ratio particles without the application of impact forces. The present invention provides therefore an attractive zero impact process that is adaptable to the production of a wide range of ceramics in particulate form.